Unibody Series · Subwoofer
Penn PA-S21
21.0″ Subwoofer · Carbon-Fiber Unibody
Flagship 21″ infra-bass for concert and stadium use, on a hybrid balanced/extended alignment.
Specifications
Engineered, then verified.
Every figure on this page traces to this cabinet’s design data in the Penn Audio Speaker Lab, where it’s modeled as a complete system and verified before production.
| Configuration | Subwoofer, vented bass reflex (front slot port) |
|---|---|
| Frequency response (−10 dB) | 24.5 Hz – 18 kHz |
| Frequency response (−3 dB) | 28.8 Hz – 18 kHz |
| Cabinet tuning Fb | 29.7 Hz |
| Sensitivity (1 W / 1 m) | 96.32 dB SPL |
| Maximum SPL (thermal) | 128.9 dB @ 1 m |
| Power handling (AES) | 1800 W |
| Nominal impedance | 4.0 Ω |
| LF transducer | 21.0″ neodymium driver |
| Recommended LP | 70 Hz LR4 (outboard DSP) |
| Enclosure | One-piece carbon-fiber composite Unibody (design) |
| Dimensions (W × H × D) | 640 × 780 × 720 mm |
| Net internal volume | 250.0 L |
| Net weight | 58.0 kg |
| Rigging | M10 HeliCoil 4-point fly grid on top, bottom, left and right faces |
| Connectors | 2 × Neutrik Speakon NL4MP, parallel-wired |
| Finish | 2K polyurethane UV-stable clear coat, semi-matte |
Inside the design
Why it’s built this way.
Carbon-fiber Unibody design
Designed as a one-piece carbon-fiber composite Unibody — a stiff, light shell engineered to keep panel resonances clear of the passband while holding weight down for a cabinet this size.
Front-loaded port
The vent fires from the front face, so the box tuning is designed to behave consistently regardless of how the sub is oriented or how close it sits to a wall or floor.
Slide-in service
The driver is designed to mount on a slide-in baffle: pull the baffle, service the driver at a bench, slide it back — the Unibody shell stays closed.
Matched transducers
Drivers are selected and matched in-house for a consistent voicing curve and a coherent impedance class across the line.
Penn Audio
Hear the PA-S21 on your system.
Book a demo, or download the full datasheet.